Technical Field
The present invention relates to a three-dimensional model data generation device and a three-dimensional model data generation method for generating three-dimensional model data for making a three-dimensional model including a plurality of structural elements by forming layers of a material, such as a resin, as well as a program for causing a computer to carry out the three-dimensional model data generation method.
Background Art
In recent years, along with the advancement of medical equipment (such as a multi-detector CT), high quality three-dimensional images are being used in diagnostic imaging. Analyzing such a three-dimensional image facilitates understanding three-dimensional shapes of various organs in the body, and also allows understanding relative positional relationships and three-dimensional structures of tissues, such as an artery, a vein, a tumor, etc., in an organ. In this case, a certain organ and certain structural elements in the organ are extracted using various image processing algorithms, and the three-dimensional shape is projected on a two-dimensional plane using a display technique, such as volume rendering, for understanding of the three-dimensional structure.
On the other hand, a three-dimensional model making device for making a three-dimensional model based on three-dimensional data representing a three-dimensional shape of an object has been proposed. This three-dimensional model making device generates, based on three-dimensional data, data in the STL (Standard Triangulated Language) format, which is a data format representing a three-dimensional object by covering the surface of a solid model with triangular patches, generates contour data (cross-sectional data) by slicing the STL data in the horizontal direction, and forms layers of a hardened material one on top of the other according to the cross-sectional data to thereby make a three-dimensional model.
In order to provide the surface of such a three-dimensional model with a pattern when the three-dimensional model is made, a technique of making a three-dimensional model by adding a pattern to three-dimensional data has been proposed (see Japanese Unexamined Patent Publication No. 2011-056697 (hereinafter, Patent Document 1)). Further, a technique for facilitating coloring of a three-dimensional model by forming a textured pattern on the surface of the three-dimensional model after the three-dimensional model is made has been proposed (see Japanese Unexamined Patent Publication No. 2002-331592 (hereinafter, Patent Document 2)).
Such three-dimensional model making devices can freely make a model having a shape that cannot be made with a resin molding method, such as extrusion molding, and are used to make prototypes of parts, such as a connector, to make a mold for injection molding, to make a model for the purpose of shape checking, etc.
Further, the three-dimensional model making devices are beginning to be used in the medical field to make a three-dimensional model of an organ, a bone, etc., based on three-dimensional images obtained by the above-described CT, as well as magnetic resonance imaging (MRI), and the like (see Japanese Unexamined Patent Publication No. 2002-040928 (hereinafter, Patent Document 3)). When a three-dimensional model of an organ is made with the three-dimensional model making device, the organ of which the three-dimensional model is to be made is extracted from a three-dimensional image to make the three-dimensional model of the extracted organ. Also, a three-dimensional model that allows checking structural elements, such as blood vessels, in the organ can be made. Such a three-dimensional model that allows checking the interior of an organ is made based on three-dimensional model data that is generated by extracting the organ and structural elements, such as blood vessels, from a three-dimensional image, generating surface data representing the surface of the organ and surface data of the structural elements, and combining these surface data.
For example, the liver includes three types of blood vessels including the hepatic artery, the hepatic vein and the portal vein, and the lungs include similar structural elements, such as the pulmonary artery, the pulmonary vein and the trachea. In the case of the liver, a three-dimensional model that allows recognizing the structural elements, such as the hepatic artery, the hepatic vein and the portal vein, in the liver is made by cutting away a part of the surface of the liver. In the case of the lungs, a three-dimensional model that allows recognizing the structural elements, such as the pulmonary artery, the pulmonary vein and the trachea, in the lungs is made by cutting away a part of the surface of the lungs.